According to various aspects, systems and methods are provided for secure communication between a passive sensor node and a reader. A passive sensor node may be used for monitoring in a variety of situations. A reader may power the passive sensor while communicating with the passive sensor. In some scenarios, it may be necessary or desirable to provide security between the passive sensor and the reader. According to one aspect, the reader may send a first message initiating communication with the passive sensor, which may respond with a second message including encrypted data. An authorized reader may decrypt the data and respond with data encrypted based on the second message in a third message, which may be used by the device to authenticate the reader.